A spirometer is a device used to provide an indication of lung capacity by measuring a complete exhaled breath. Typically, the spirometer has a mouthpiece connected via a hose to means to measure the volume of exhaled air. The person places his mouth over the mouthpiece and exhales through the hose to obtain a lung capacity measurement.
Typically, the mouthpiece is a separate disposable tube, commonly made of cardboard. The tube is fairly rigid to prevent collapse during testing and also to assist in obtaining a proper seal when mated with a socket in the spirometer hose. In U.S. Pat. No. 3,749,087, a disposable mouthpiece is shown which has a cylindrical construction and has an enlarged portion insertable into an interface chamber and a reduced diameter portion usable as a mouthpiece. The mouthpiece is specialized in that it is manufactured with an integral container which acts as a bladder to accept a breath and displace air in a spirometer chamber to obtain the lung capacity measurement. Such a mouthpiece is costly to produce, and is quite bulky to store. Additionally, since the tube is fairly rigid, it consumes substantial space on disposal.